1. Field of the Invention
This invention relates to valves and has particular reference to fluid control valves in which a minimum amount of energy is required to move a valve between open and closed condition. Although the invention is particularly applicable to the control of water flow in automatic sprinkling systems, it is also applicable to other types of fluid control systems and solenoid operated devices.
2. Description of the Prior Art
In automatic water sprinkling systems, valves may be distributed in different locations in areas to be sprinkled and may be actuated by electromagnetic actuators under control of a timer or timers to open the valves at different selected times.
Water pressures on the order of 80 to 100 pounds per square inch are normally encountered in the operation of such systems. Therefore, sprinkler valves must be of sufficient size and ruggedness to safely and reliably handle such pressures at rates of flow required for sprinkling systems without leakage or malfunction. Heretofore, such valves required electromagnetic actuators of considerable strength or required relatively expensive pilot operated fluid actuators, for proper and reliable actuation, thereby requiring relatively large electric currents for energization or critical pilot valves of small size and force. This, in turn, precluded the use of batteries which might be otherwise located directly adjacent to the valves, but required that the valve actuators be connected to sources of current, such as regular household supply terminals, by wire conductors. Since the water control valves may be widely distributed throughout an area to be sprinkled, such conductors must be strung, either under ground or over the ground, between the various valves and the current supply source.
Attempts have been made, heretofore, to develop simple valves which require a minimum amount of control effort in order to adequately control the flow of fluid under pressures comenserate with those found in the usual water supply systems. For example, the U.S. Pat. Nos. 2,747,611 issued to E. E. Hewitt on May 29, 1956 and 2,764,181 issued to R. R. Richolt on Sept. 26, 1956 discloses a piston type valve element with longitudinally extending grooved sections surrounded by sealing O-rings held in grooves in a valve body. Shifting of the valve element to move the grooved section out from under an O-ring will seal the valve passage. However, such O-rings must be placed under sufficient radial tension to adequately seal against leakage when the valve is closed and this incures a frictional engagement between the valve element and the O-ring which increases the resistance to movement of the valve element and thus requires appreciable force to actuate the valve element. Also, other sliding bearing supports are provided for slideably supporting the valve elements and these also add to the frictional resistance to movement of the valve element.